1. Field of the Invention
The present invention relates to a tool for beveling an end of a pipe cut on site during a pipe laying installation.
2. Description of the Prior Art
Sections of pipe that are to be utilized in subsurface applications such as drainpipes, cable pipes, gas line pipes, and oil pipelines are cut to specific lengths when they are manufactured. During the pipe section fabrication process, particularly with large diameter pipes, the sections of pipe are often created with an enlarged bell or socket connection at one end, and are beveled or chamfered at the other end. Sections of pipe must be beveled so as to accommodate an O-ring gasket to ensure a fluid-tight connection between the adjacent pipe sections. An enlarged socket or bell coupling is required to prevent the O-ring from being damaged during the laying of the pipe. When a pipe line is laid the beveled end of each section of pipe is inserted into the larger socket or bell connection end of an adjacent pipe section. Each new section of pipe is then forced longitudinally toward the prior sections that have already been laid in position.
It is particularly important for the bevel to be properly formed for large diameter pipes, since the force required to push each pipe section into sealing engagement with the prior sections is too great to be applied manually. The pipe sections are typically pushed into position using levers or a machine bucket. As a consequence, any excess resistance that might be present as a result of an O-ring being damaged cannot be felt when large pipe sections are forced together. Installers can therefore only hope that a leakproof installation has been achieved during assembly of the pipe sections together.
While the machinery available to form bevels or chamfers during the manufacture of the pipe sections reliably produces bevels at the proper angle and depth, there are circumstances in which bevels need to be performed on pipe sections in the field at the job site. Specifically, it is necessary to cut pipes on site whenever plans call for a “T”, a “Y”, or at the end of a run at a manhole or other junction which requires cutting the pre-cut and pre-beveled pipe sections at the pipeline installation site.
Currently, pipe is typically cut with a power saw having a rotary blade at a job site. This leaves a rough cut pipe end that is roughly perpendicular to the axis of the pipe. The operator then utilizes a hand device, such as a file or grinder attached to the side of the saw blade in order to produce a bevel on the cut end of the pipe. This can be dangerous if the blade is not designed to be used as a grinder. There have been instances of composite, cut off wheels exploding due to the erosion of the reinforcement and abrasive on the sides of the blades. Furthermore, it is very difficult to manually hold the saw so as to produce a uniform bevel of a specific chamfer angle throughout the entire perimeter of the cut end of the pipe. As a consequence, the bevel can be too shallow or two deep.
If a bevel is cut too shallow, the gap for the O-ring is too small and the O-ring cannot fit into it to create a seat during the coupling of two pipe sections. On the other hand, if the bevel is so deep that a sharp edge is produced on the pipe end, the O-ring can be cut when the beveled end of the pipe is forced into the bell or socket connection of an adjacent pipe. In either case, the O-ring is improperly seated and leaking can occur at the pipe coupling.
Furthermore, pipes are supplied with varying wall thicknesses. As a consequence, the amount of a bevel must be changed. If too much bevel is attempted then a fine and easily damaged edge is produced on the pipe which creates additional problems. In addition, if an edge is created, any powered hand beveler will lose one of the guiding surfaces and an irregular cut will be produced. In some instances the amount of material to be removed is so much that it becomes necessary to make two cuts. This requires adjustment of the depth of cut. Clearly, a quick and simple adjustment system for a beveling tool is necessary if end-users are to complete the pipe beveling job properly.
One device has been produced which is a beveling tool that attaches to the arbor bolt of a power saw. This device is sold by PB Tools, address 4431 Sunnyside Boulevard, Maryville Wash. 98 270. This device has an annular, barrel-shaped body within which a core having a beveling cutter head is located. The shank of the core is externally threaded and fits through a central, axial opening in the body. Positioning end nuts are threadably engaged on the core shank and are loosened to allow advancement and withdrawal of the core within the body to vary the extent to which the beveling cutter head protrudes from the outboard end of the tool body. When, in the operator's judgment, the extent of exposure of the beveling cutter head is proper, the positioning nuts are tightened to clamp the core to the body and longitudinally immobilize it relative to the body.
One significant disadvantage of this tool is that the adjustments are not easily reproducible. That is, there is no reliable way for the operator to return the beveling cutter head to a previously selected position of extension from the outboard end of the tubular body. Consequently, beveling depths are not readily reproducible using this tool since there is no easy, reliable way of changing the depth of the bevel cut and then returning to a prior bevel cut setting.
Furthermore, loosening and tightening of the positioning nuts is rather difficult. Access to one of the positioning nuts is through a slot in the body which is not easily accessible. Moreover, wrenches of two different sizes must be employed in separate operations to untighten both positioning nuts and then retighten them.
A further disadvantage of this tool is that head is mounted to the arbor of a power saw by a threaded inboard shank that has the same pitch and diameter of a conventional arbor saw bolt. Because of the relatively large balk of the tool, as contrasted to an arbor bolt head, there is a considerable longitudinal bending moment applied to the inboard shank of the tool during the beveling operation. Consequently, the mounting shank of the tool is quite likely to break, and frequently does so.
A further disadvantage of this tool is that it cannot be attached to and detached from a power saw without uncoupling the attachment of the saw to the saw blade arbor. Consequently, the tool cannot be quickly and easily removed from or attached to a conventional power saw. Moreover, the coupling arrangement employed limits use of the tool to attachment to only a particular type of power saw having a particular type of saw blade mounting.